I've heard several different pronunciations over the years, several from
people who "should know" and were quite adamant about it. They can't
all be right...

Unless of course there are several equally valid pronunciations.

Entirely possible, but in that case the adamant folk still can't all be
right because they're saying this is *the* way it's pronounced...
Scoan or skon?

One of them wee cakey biscuit thingies with heaps of jam and cream and a
pot of tea! ;-)

Having been born and raised in South East England, moved to the Midlands
for University, shared flats with Northerners and then moved to Scotland
my own set of favoured pronunciations is quite a mixed bag! Add that to
an unusual accent (one of those cases where the first time you hear a
recording of yourself you've no idea who it is, and it sounds totally
different inside) and it's fairly atypical for people to place where I
come from just from my speech.